Hydrogen specific heat

Oxygen specific heat at constant volume Nitrogen specific heat at constant volume Hydrogen specific heat at constant volume Water specific heat at constant volume Oxygen thermal conductivity Nitrogen conductivity Hydrogen thermal conductivity Water thermal conductivity... 

Physical Properties. Physical properties of anhydrous hydrogen fluoride are summarized in Table 1. Figure 1 shows the vapor pressure and latent heat of vaporization. The specific gravity of the Hquid decreases almost linearly from 1.1 at —40°C to 0.84 at 80°C (4). The specific heat of anhydrous HF is shown in Figure 2 and the heat of solution in Figure 3. 

Fig. 2. Specific heat of Hquid anhydrous hydrogen fluoride (5,16). To convert to cal, divide by 4.184.

The specific heat of aqueous solutions of hydrogen chloride decreases with acid concentration (Fig. 4). The electrical conductivity of aqueous hydrogen chloride increases with temperature. Equivalent conductivity of these solutions ate summarized in Table 8. Other physicochemical data related to... 

Fig. 4. Specific heat of aqueous solutions of hydrogen chloride.

Thermodynamic data on H2, the mixed hydrogen—deuterium molecule [13983-20-5] HD, and D2, including values for entropy, enthalpy, free energy, and specific heat have been tabulated (16). Extensive PVT data are also presented in Reference 16 as are data on the equihbrium—temperature... 

Problems sometimes occur in trying to minimize the temperature difference at the cold end of the heat exchanger, particularly if the specific heat of the warm fluid decreases with decreasing temperature as is the case with gaseous hydrogen. 

The hydrogen content, heat of combustion, specific heat, and thermal conductivity data herein were abstracted from Bureau of Standards MisceUaneous Pubhcation 97, Thermal Propei tie.s of Petroleum Products. These data are widely used, although other correlations have appeared, notably that by Linden and Othmer Chem. Eng. 54[4, 5], April and May, 1947). 

Water has many unusual properties in addition to its high boiling point. As pointed out in Chapter 8, it has a very high specific heat, 4.18 J/g °C. Its heat of vaporization per gram, 2.26 kj/g, is the highest of all molecular substances. Both of these properties reflect the hydrogen-bonded structure of the liquid. Many of these bonds have to be broken when the liquid is heated all of them disappear on boiling. 

At the other temperature extreme we have the measurements of specific heats executed at the temperatures of liquefied gases. A known mass of the substance is dropped into liquid carbon dioxide (— 78°), oxygen (— 183°), or hydrogen (— 250°), and the volume of gas liberated is measured. 

The specific heats of diamond and graphite are reduced to 19 and Tx() respectively between the ordinary temperature and the boiling-point of liquid hydrogen the specific heats of the substances between the temperatures of liquid air and liquid hydrogen are in fact less than those of any other substances, even less than that of a gas at constant volume. 

This remarkable result has been verified by experimental measurements of specific heats at very low temperatures, viz., in liquid air and liquid hydrogen (cf. references in Chap. I.). It was formerly believed that the specific heats of solids approached small positive limiting values at the absolute zero, but the form of the curve at very low temperatures alters appreciably, and it may be inferred that the specific heat is vanishingly small at... 

The properties of the hydrogen molecule and molecule-ion which are the most accurately determined and which have also been the subject of theoretical investigation are ionization potentials, heats of dissociation, frequencies of nuclear oscillation, and moments of inertia. The experimental values of all of these quantities are usually obtained from spectroscopic data substantiation is in some cases provided by other experiments, such as thermochemical measurements, specific heats, etc. A review of the experimental values and comparison with some theoretical... 

This result is independently verified by Dennison (17) who has recently given a satisfactory theory of the specific heat of hydrogen. The observed specific heat as interpreted by Dennison requires that I0 be equal to 0.464 X 10 40 g. cm.2. The very recent measurements by Cornish and Eastman (18) of the specific heat of hydrogen from the velocity of sound are said to agree very well with Dennison s theory if I0 be given the value of 0.475 X 10-40 g. cm.2. 

Other constants of the hydrogen molecule obtained from our data are the lowest resonance potential = 11.61 volts the frequency of infinitesimal vibration co0 in the normal state = 4260.cm. 1, which is in fair agreement with the value 4880.cm. 1, obtained by Kemble and Van Vleck5 from specific heat data and the value of x< >o (coefficient of n2) for the normal state = 112.5. cm."1. 

A special attention is to be devoted to copper, which is very often used in a cryogenic apparatus. The low-temperature specific heat of copper is usually considered as given by c = 10-5 T [J/g K], However, an excess of specific heat has been measured, as reported in the literature [59-69], For 0.03 K < T< 2K, this increase is due to hydrogen or oxygen impurities, magnetic impurities (usually Fe and Mn) and lattice defects [59-66], The increase of copper specific heat observed in the millikelvin temperature range is usually attributed to a Schottky contribution due to the nuclear quadrupole moment of copper [67,68],... 

Soon after Dennison had deduced from the specific-heat curve that ordinary hydrogen gas consists of a mixture of two types of molecule, the so-called ortho and para hydrogen, a similar state of affairs in the case of iodine gas was demonstrated by direct experiment by R. W. Wood and F. W. Loomis.1 In brief, these experimenters found that the iodine bands observed in fluorescence stimulated by white light differ from those in the fluorescence excited by the green mercury line X 5461, which happens to coincide with one of the iodine absorption lines. Half of the lines are missing in the latter case, only those being present which are due to transitions in which the rotational quantum number of the upper state is an even integer. In other words, in the fluorescence spectrum excited by X 5461 only those lines appear which are due to what we may provisionally call the ortho type of iodine molecule. 

Liquid anhydrous hydrogen fluoride, specific heat of, 14 3 Liquid argon, shipping, 17 364 Liquid atomization... 

The theoretical value of the frequency of vibration, depending on the curvature of the cmrve at its minimum, is naturally more uncertain. Calculation shows that the curve gives a frequency of vibration of 5300 cm. S about 20% higher than the value 4360 cm. from experiment. As for the moment of inertia, while it is larger than most of the values from specific heat theories, it is in accord with the larger values which have been found by Richardson and Tanaka from analysis of the hydrogen bands. 

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